The present invention relates to an angular velocity sensor used for car navigation and control on an orientation of a vehicle.
An angular velocity sensor includes a tuning-fork-type vibrator made of crystal vibrated by a driving electrode disposed on the vibrator. A deflection amount of the vibrator due to Coriolis force is represented as an electric signal through a detection electrode disposed on the vibrator. The Coriolis force, when an angular velocity is applied to the vibrator, is generated orthogonally to the vibration direction of the tuning-fork.
For example, the angular velocity sensor includes a bulk-type of the tuning-fork-type vibrator made of crystal or the like. The vibrator is formed by removing an unnecessary portion from a material having an area larger than that of the vibrator by etching or cutting. A supporting part supports the tuning fork and makes the tuning folk independent of the outside regarding vibration. Sintered material or crystal material is expensive and requires a large amount of processing to be formed into a complex shape. Therefore, a method of supporting and fixing the tuning-fork-type vibrator using an independently-produced member is considered so as to reduce material cost as low as possible and to allow easy manufacturing.
However, the tuning-fork-type vibrator made of this kind of material cannot employ a brazing method due to the composition of the material. As a result, the vibrator is adhered with a resin-based adhesive to be supported and fixed.
Referring to FIG. 7 through FIG. 9, a conventional angular velocity sensor will be explained. In FIG. 7 through FIG. 9, reference numeral 1 denotes a tuning-fork-type vibrator made of crystal or piezoelectric ceramics. An angular velocity sensor element comprises a base 1c formed at one side of a pair of legs 1a, 1b, and a driving electrode and a detecting electrode, which are not shown, are formed on legs 1a, 1b. Reference numeral 2 denotes a supporting block which is made of metal, ceramic, crystal, or resin material and is mounted on a board 5 including a processing circuit, which is not shown. The end surface of the base 1c of the tuning-fork-type vibrator 1 is supported and fixed to a side of the supporting block 2 with an adhesive 7.
In the conventional angular velocity sensor, the tuning-fork-type vibrator 1 of a beam structure has an end surface fixed to the supporting block 2 with the adhesive 7. Therefore, the sensor has weak adhering strength with a lot of variation of the adhering strength, and is not manufactured with a high level of reliability to withstand shock applied from the outside.
It is an object of the present invention to provide an angular velocity sensor that has high strength mounting of a tuning-fork-type vibrator to a support block and high stability of supporting the vibrator.
To achieve the object, in the angular velocity sensor of the present invention, a mounting recess having a shape close to that of a cross section of a base of the tuning-fork-type vibrator is formed in the support block, and the base of the tuning-fork-type vibrator is embedded and fixed into the mounting recess with an adhesive.
This structure allows the tuning-fork-type vibrator to be adhered and fixed to the support block with a stable strength for shock and stress.